diff --git a/src/main/kotlin/me/gergo/Aoc01.kt b/src/main/kotlin/me/gergo/Aoc01.kt
index 59df70e..fe4b74a 100644
--- a/src/main/kotlin/me/gergo/Aoc01.kt
+++ b/src/main/kotlin/me/gergo/Aoc01.kt
@@ -23,6 +23,6 @@ fun main() {
         .sumOf { it.calories })
 }
 
-class Elf {
+private class Elf {
     var calories = 0;
 }
\ No newline at end of file
diff --git a/src/main/kotlin/me/gergo/Aoc02.kt b/src/main/kotlin/me/gergo/Aoc02.kt
index 76511c9..52b9c7a 100644
--- a/src/main/kotlin/me/gergo/Aoc02.kt
+++ b/src/main/kotlin/me/gergo/Aoc02.kt
@@ -11,7 +11,7 @@ fun main() {
 }
 
 enum class Choice { Rock, Paper, Scissors }
-data class Guide(val opponent: Choice, val my: Choice) {
+private data class Guide(val opponent: Choice, val my: Choice) {
     fun score(): Int = scoreFor(my) + scoreForOutcomeOf(opponent, my)
 
     private fun scoreFor(c: Choice): Int = c.ordinal + 1
@@ -24,7 +24,7 @@ data class Guide(val opponent: Choice, val my: Choice) {
     }
 }
 
-fun parseGuide(line: String): Guide {
+private fun parseGuide(line: String): Guide {
     val tokens = line.split(" ")
     val opponent = when (tokens[0]) {
         "A" -> Rock
diff --git a/src/main/kotlin/me/gergo/Aoc02b.kt b/src/main/kotlin/me/gergo/Aoc02b.kt
index 84e2b78..5e587cf 100644
--- a/src/main/kotlin/me/gergo/Aoc02b.kt
+++ b/src/main/kotlin/me/gergo/Aoc02b.kt
@@ -13,8 +13,8 @@ fun main() {
 
 private val Choices = Choice.values()
 
-enum class Result { Lose, Draw, Win }
-data class Guide2(val opponent: Choice, val result: Result) {
+private enum class Result { Lose, Draw, Win }
+private data class Guide2(val opponent: Choice, val result: Result) {
     fun score(): Int = scoreFor(pickChoiceFor(opponent, result)) + scoreFor(result)
 
     private fun scoreFor(r: Result): Int = when (r) {
@@ -31,7 +31,7 @@ data class Guide2(val opponent: Choice, val result: Result) {
     }
 }
 
-fun parseGuide2(line: String): Guide2 {
+private fun parseGuide2(line: String): Guide2 {
     val tokens = line.split(" ")
     val opponent = when (tokens[0]) {
         "A" -> Rock
diff --git a/src/main/kotlin/me/gergo/Aoc03.kt b/src/main/kotlin/me/gergo/Aoc03.kt
index a76a743..cf42de0 100644
--- a/src/main/kotlin/me/gergo/Aoc03.kt
+++ b/src/main/kotlin/me/gergo/Aoc03.kt
@@ -12,22 +12,22 @@ fun main() {
     println(results)
 }
 
-data class Rucksack(val c1: String, val c2: String) {
+private data class Rucksack(val c1: String, val c2: String) {
     fun priorityOfSharedType() = priorityOf(sharedType()) // For Part One
 
     private fun sharedType(): Char = c1.toCharArray().intersect(c2.toCharArray().toSet()).first()
 }
 
-fun parseRucksack(line: String): Rucksack {
+private fun parseRucksack(line: String): Rucksack {
     return Rucksack(line.substring(0, line.length / 2), line.substring(line.length / 2))
 }
 
-fun priorityOfSharedType(group: Iterable<Rucksack>): Int {
+private fun priorityOfSharedType(group: Iterable<Rucksack>): Int {
     val sharedType = group.map { (it.c1 + it.c2).toCharArray().toSet() }.reduce { acc, r -> acc.intersect(r) }.first()
     return priorityOf(sharedType)
 }
 
-fun priorityOf(type: Char): Int {
+private fun priorityOf(type: Char): Int {
     val d = type.code
     return if (d >= 'a'.code && d <= 'z'.code) d - 'a'.code + 1
     else d - 'A'.code + 27
diff --git a/src/main/kotlin/me/gergo/Aoc04.kt b/src/main/kotlin/me/gergo/Aoc04.kt
index d74bad3..1e64b81 100644
--- a/src/main/kotlin/me/gergo/Aoc04.kt
+++ b/src/main/kotlin/me/gergo/Aoc04.kt
@@ -11,12 +11,12 @@ fun main() {
     println(results)
 }
 
-data class Assignment(val first: IntRange, val second: IntRange) {
+private data class Assignment(val first: IntRange, val second: IntRange) {
     fun fullyContains() = first.minus(second).isEmpty() || second.minus(first).isEmpty()
     fun overlaps() = first.minus(second).size < first.count() || second.minus(first).size < second.count()
 }
 
-fun parseAssignment(line: String): Assignment {
+private fun parseAssignment(line: String): Assignment {
     val ranges = line.split(",").map {
         val range = it.split("-").map(String::toInt)
         range[0]..range[1]
diff --git a/src/main/kotlin/me/gergo/Aoc05.kt b/src/main/kotlin/me/gergo/Aoc05.kt
index de7d9ae..32db9b3 100644
--- a/src/main/kotlin/me/gergo/Aoc05.kt
+++ b/src/main/kotlin/me/gergo/Aoc05.kt
@@ -16,17 +16,17 @@ fun main() {
     stacks.forEach { print(it.peek()) }
 }
 
-typealias CrateStack = Stack<Char>
+private typealias CrateStack = Stack<Char>
 
-data class Instruction(val quantity: Int, val fromStack: Int, val toStack: Int) {}
+private data class Instruction(val quantity: Int, val fromStack: Int, val toStack: Int) {}
 
-fun parseStacksAndInstructions(lines: List<String>): Pair<List<CrateStack>, List<Instruction>> {
+private fun parseStacksAndInstructions(lines: List<String>): Pair<List<CrateStack>, List<Instruction>> {
     val stacks = parseStacks(lines.subList(0, lines.indexOf("") - 1))
     val instructions = lines.subList(lines.indexOf("") + 1, lines.size).map(::parseInstruction)
     return Pair(stacks, instructions)
 }
 
-fun parseStacks(lines: List<String>): List<CrateStack> {
+private fun parseStacks(lines: List<String>): List<CrateStack> {
     val stackCount = (lines[0].length + 1) / 4
     val result = List(stackCount) { Stack<Char>() }
     for (i in lines.size - 1 downTo 0) {
@@ -41,7 +41,7 @@ fun parseStacks(lines: List<String>): List<CrateStack> {
     return result
 }
 
-fun parseInstruction(line: String): Instruction {
+private fun parseInstruction(line: String): Instruction {
     val m = Regex("move (\\d+) from (\\d+) to (\\d+)").matchEntire(line)!!
     return Instruction(m.groupValues[1].toInt(), m.groupValues[2].toInt(), m.groupValues[3].toInt())
 }
diff --git a/src/main/kotlin/me/gergo/Aoc07.kt b/src/main/kotlin/me/gergo/Aoc07.kt
index ec09ac2..e415af4 100644
--- a/src/main/kotlin/me/gergo/Aoc07.kt
+++ b/src/main/kotlin/me/gergo/Aoc07.kt
@@ -40,7 +40,7 @@ fun main() {
     println("To delete: $toDelete, totalSize=${toDelete.totalSize()}")
 }
 
-fun parseCommandLine(line: String): CommandLine {
+private fun parseCommandLine(line: String): CommandLine {
     return if (line == "$ ls") Ls
     else if (line.startsWith("$ cd")) Cd(line.substring(5))
     else if (line.startsWith("dir ")) DirectoryOutput(line.substring(4))
@@ -50,13 +50,13 @@ fun parseCommandLine(line: String): CommandLine {
     }
 }
 
-sealed interface CommandLine
-object Ls : CommandLine {}
-data class Cd(val dirName: String) : CommandLine {}
-data class DirectoryOutput(val name: String) : CommandLine {}
-data class FileOutput(val name: String, val size: Int) : CommandLine {}
+private sealed interface CommandLine
+private object Ls : CommandLine {}
+private data class Cd(val dirName: String) : CommandLine {}
+private data class DirectoryOutput(val name: String) : CommandLine {}
+private data class FileOutput(val name: String, val size: Int) : CommandLine {}
 
-data class FileNode(val name: String, val size: Int, var parent: FileNode?, val children: MutableList<FileNode>) {
+private data class FileNode(val name: String, val size: Int, var parent: FileNode?, val children: MutableList<FileNode>) {
 
     fun isDirectory() = children.size > 0
 
diff --git a/src/main/kotlin/me/gergo/Aoc08.kt b/src/main/kotlin/me/gergo/Aoc08.kt
index 6886873..eb2820e 100644
--- a/src/main/kotlin/me/gergo/Aoc08.kt
+++ b/src/main/kotlin/me/gergo/Aoc08.kt
@@ -11,7 +11,7 @@ fun main() {
     println("Max scenic score: ${trees.maxScenicScore()}") // Part Two
 }
 
-class Trees(lines: List<String>) {
+private class Trees(lines: List<String>) {
     private val forest: Array<IntArray>
     private val width: Int
     private val height: Int
diff --git a/src/main/kotlin/me/gergo/Aoc09.kt b/src/main/kotlin/me/gergo/Aoc09.kt
index 18fab08..05d840b 100644
--- a/src/main/kotlin/me/gergo/Aoc09.kt
+++ b/src/main/kotlin/me/gergo/Aoc09.kt
@@ -18,13 +18,13 @@ fun main() {
     println("Positions visited by tail: ${ropeField.positionsVisitedByTail().count()}")
 }
 
-enum class Direction { L, R, U, D }
-data class RopeStep(val dir: Direction, val steps: Int)
-data class Position(val x: Int, val y: Int) {
+private enum class Direction { L, R, U, D }
+private data class RopeStep(val dir: Direction, val steps: Int)
+private data class Position(val x: Int, val y: Int) {
     fun distanceFrom(o: Position) = max(abs(x - o.x), abs(y - o.y))
 }
 
-class Rope(internal val knots: MutableList<Position>) {
+private class Rope(internal val knots: MutableList<Position>) {
 
     fun head() = knots[0]
     fun tail() = knots[knots.size - 1]
@@ -56,7 +56,7 @@ class Rope(internal val knots: MutableList<Position>) {
     }
 }
 
-class RopeField(private val width: Int, private val height: Int, ropeLength: Int) {
+private class RopeField(private val width: Int, private val height: Int, ropeLength: Int) {
     private val rope = Rope(MutableList(ropeLength) { Position(0, 0) })
     private val tailPositions = mutableListOf<Position>()
 
@@ -81,7 +81,7 @@ class RopeField(private val width: Int, private val height: Int, ropeLength: Int
     fun positionsVisitedByTail() = tailPositions.toSet()
 }
 
-fun parseRopeStep(line: String): RopeStep {
+private fun parseRopeStep(line: String): RopeStep {
     val (dir, steps) = line.split(" ")
     return RopeStep(Direction.valueOf(dir), steps.toInt())
 }
diff --git a/src/main/kotlin/me/gergo/Aoc10.kt b/src/main/kotlin/me/gergo/Aoc10.kt
index 6e2a9a2..81cf8ce 100644
--- a/src/main/kotlin/me/gergo/Aoc10.kt
+++ b/src/main/kotlin/me/gergo/Aoc10.kt
@@ -19,9 +19,9 @@ fun main() {
     CRT(40, 6, cpu).draw()
 }
 
-sealed class Instr(val duration: Int)
-object Noop : Instr(1)
-data class Addx(val value: Int) : Instr(2)
+private sealed class Instr(val duration: Int)
+private object Noop : Instr(1)
+private data class Addx(val value: Int) : Instr(2)
 
 private class CPU(private val instructions: List<Instr>) {
     private var instructionPointer = 0
@@ -56,7 +56,7 @@ private class CRT(private val width: Int, private val height: Int, private val c
     }
 }
 
-fun parseInstr(line: String): Instr {
+private fun parseInstr(line: String): Instr {
     val tokens = line.split(" ")
     return if (tokens[0] == "noop") Noop
     else Addx(tokens[1].toInt())
diff --git a/src/main/kotlin/me/gergo/Aoc11.kt b/src/main/kotlin/me/gergo/Aoc11.kt
index a2040fc..271acaa 100644
--- a/src/main/kotlin/me/gergo/Aoc11.kt
+++ b/src/main/kotlin/me/gergo/Aoc11.kt
@@ -7,7 +7,7 @@ private const val Rounds = 10000
 
 /**
  * Note: this only has Part Two, as I did Part One with a naiive solution that probably takes all the memory in the world, multiplying horribly large
- * BigDecimals :) The trick in this one is to remember but delay the computation for as long as possible. As we're only really interested in whether
+ * BigDecimals :) The trick in this one is to remember to delay the computation for as long as possible. As we're only really interested in whether
  * the result at the end of a long chain of operations is divisible by N, we can modulo N per every operation - but we must do that for each monkey
  * individually, which means we must remember the computation chain (Items.operations in this implementation)!
  * 
@@ -38,19 +38,6 @@ fun main() {
     println("Level of monkey business: $result")
 }
 
-fun lcm(a: Int, b: Int) = a * (b / gcd(a, b))
-
-fun gcd(a: Int, b: Int): Int {
-    var a0 = a
-    var b0 = b
-    while (b0 > 0) {
-        val temp = b0
-        b0 = a0 % b0
-        a0 = temp
-    }
-    return a0
-}
-
 private class Monkey(val name: Int, val items: Queue<Item>, val operation: Operation, val divisor: Int, val throwToTrue: Int, val throwToFalse: Int) {
     var inspections = 0L
 
diff --git a/src/main/kotlin/me/gergo/Aoc12.kt b/src/main/kotlin/me/gergo/Aoc12.kt
index e0a8e2b..631404e 100644
--- a/src/main/kotlin/me/gergo/Aoc12.kt
+++ b/src/main/kotlin/me/gergo/Aoc12.kt
@@ -58,58 +58,4 @@ private operator fun Array<CharArray>.set(c: Coordinate, value: Char) {
     this[c.y][c.x] = value
 }
 
-data class Coordinate(val x: Int, val y: Int)
-
-fun aStar(
-    start: Coordinate, goal: Coordinate,
-    neighborFn: (Coordinate) -> Sequence<Coordinate>,
-    heuristicFn: (Coordinate) -> Double,
-    distanceFn: (Coordinate, Coordinate) -> Double
-): List<Coordinate> {
-    val openSet = mutableSetOf(start)
-    val cameFrom = mutableMapOf<Coordinate, Coordinate>()
-
-    val gScore = mutableMapOf<Coordinate, Double>()
-    gScore[start] = 0.0
-
-    val fScore = mutableMapOf<Coordinate, Double>()
-    fScore[start] = heuristicFn(start)
-
-    while (openSet.isNotEmpty()) {
-        val current = openSet.minBy { fScore.getOrDefault(it, POSITIVE_INFINITY) }
-        if (current == goal) {
-            // Path found, reconstructing
-            val result = mutableListOf(current)
-            var c: Coordinate? = current
-            while (true) {
-                c = cameFrom[c]
-                if (c == null) break
-                result.add(0, c)
-            }
-            return result
-        }
-
-        openSet.remove(current)
-        for (neighbor in neighborFn(current)) {
-            val tentativeGScore = gScore.getOrDefault(current, POSITIVE_INFINITY) + distanceFn(current, neighbor)
-            if (tentativeGScore < gScore.getOrDefault(neighbor, POSITIVE_INFINITY)) {
-                cameFrom[neighbor] = current
-                gScore[neighbor] = tentativeGScore
-                fScore[neighbor] = tentativeGScore + heuristicFn(neighbor)
-                openSet.add(neighbor)
-            }
-        }
-    }
-    return emptyList() // Path not found
-}
-
-fun neighbors(width: Int, height: Int, c: Coordinate) = sequence {
-    val x = c.x
-    val y = c.y
-    if (x > 0) yield(Coordinate(x - 1, y))
-    if (y + 1 < height) yield(Coordinate(x, y + 1))
-    if (x + 1 < width) yield(Coordinate(x + 1, y))
-    if (y > 0) yield(Coordinate(x, y - 1))
-}
-
 private fun manhattanDistance(a: Coordinate, b: Coordinate): Double = (abs(b.x - a.x) + abs(b.y - a.y)).toDouble()
diff --git a/src/main/kotlin/me/gergo/coordinates.kt b/src/main/kotlin/me/gergo/coordinates.kt
new file mode 100644
index 0000000..43117e9
--- /dev/null
+++ b/src/main/kotlin/me/gergo/coordinates.kt
@@ -0,0 +1,15 @@
+package me.gergo
+
+import kotlin.math.abs
+
+data class Coordinate(val x: Int, val y: Int)
+
+fun neighbors(width: Int, height: Int, c: Coordinate) = sequence {
+    val x = c.x
+    val y = c.y
+    if (x > 0) yield(Coordinate(x - 1, y))
+    if (y + 1 < height) yield(Coordinate(x, y + 1))
+    if (x + 1 < width) yield(Coordinate(x + 1, y))
+    if (y > 0) yield(Coordinate(x, y - 1))
+}
+
diff --git a/src/main/kotlin/me/gergo/math.kt b/src/main/kotlin/me/gergo/math.kt
new file mode 100644
index 0000000..ad7e266
--- /dev/null
+++ b/src/main/kotlin/me/gergo/math.kt
@@ -0,0 +1,14 @@
+package me.gergo
+
+fun lcm(a: Int, b: Int) = a * (b / gcd(a, b))
+
+fun gcd(a: Int, b: Int): Int {
+    var a0 = a
+    var b0 = b
+    while (b0 > 0) {
+        val temp = b0
+        b0 = a0 % b0
+        a0 = temp
+    }
+    return a0
+}
diff --git a/src/main/kotlin/me/gergo/search.kt b/src/main/kotlin/me/gergo/search.kt
new file mode 100644
index 0000000..26ca783
--- /dev/null
+++ b/src/main/kotlin/me/gergo/search.kt
@@ -0,0 +1,44 @@
+package me.gergo
+
+fun <N> aStar(
+    start: N, goal: N,
+    neighborFn: (N) -> Sequence<N>,
+    heuristicFn: (N) -> Double,
+    distanceFn: (N, N) -> Double
+): List<N> {
+    val openSet = mutableSetOf(start)
+    val cameFrom = mutableMapOf<N, N>()
+
+    val gScore = mutableMapOf<N, Double>()
+    gScore[start] = 0.0
+
+    val fScore = mutableMapOf<N, Double>()
+    fScore[start] = heuristicFn(start)
+
+    while (openSet.isNotEmpty()) {
+        val current = openSet.minBy { fScore.getOrDefault(it, Double.POSITIVE_INFINITY) }
+        if (current == goal) {
+            // Path found, reconstructing
+            val result = mutableListOf(current)
+            var c: N? = current
+            while (true) {
+                c = cameFrom[c]
+                if (c == null) break
+                result.add(0, c)
+            }
+            return result
+        }
+
+        openSet.remove(current)
+        for (neighbor in neighborFn(current)) {
+            val tentativeGScore = gScore.getOrDefault(current, Double.POSITIVE_INFINITY) + distanceFn(current, neighbor)
+            if (tentativeGScore < gScore.getOrDefault(neighbor, Double.POSITIVE_INFINITY)) {
+                cameFrom[neighbor] = current
+                gScore[neighbor] = tentativeGScore
+                fScore[neighbor] = tentativeGScore + heuristicFn(neighbor)
+                openSet.add(neighbor)
+            }
+        }
+    }
+    return emptyList() // Path not found
+}